Magnetocaloric Materials and Their Applications
05/31/2023 Kevin Kurtz

Modern advances in materials and electromagnetic circuit design can create more efficient and environmentally friendly takes on current technology. For example, magnetocaloric materials and magnetic refrigeration. The concept of magnetic refrigeration has been around since the late 1800’s, but recently it has become practical due to advances in magnetocaloric research, efficiency and magnetic field control.

Magnetocaloric materials exhibit a significant change in temperature when in the presence of a magnetic field. This phenomenon is known as the magnetocaloric effect. When a magnetocaloric material is exposed to a magnetic field, the magnetic moments of its atoms or molecules become aligned with the field, which increases the degree of order in the material. This alignment of magnetic moments requires energy, which is typically drawn from the material's thermal energy causing a decrease in temperature. The degree of temperature change depends on the strength of the magnetic field and the properties of the material.

Permanent magnet systems can be rotated or moved to vary field strength and interact with the magnetocaloric material targets. With the right circuit, these field changes can be fast and drastic. Electromagnetic coils can also be used, but often they are less efficient than the permanent magnet systems we have designed.

Some of the more commonly used magnetocaloric materials are:

  1. Gadolinium (Gd): It displays a strong magnetocaloric effect near room temperature.

  2. Magnetocaloric alloys: One example is the Gd-Si-Ge system, where the addition of silicon and germanium to gadolinium improves the properties.

  3. Other rare-earth elements, such as dysprosium (Dy), erbium (Er), and holmium (Ho), exhibit significant magnetocaloric effects. Alloys based on these elements, such as Dy-Al-Ni and Er-Fe, have been studied.

  4. Certain manganese-based compounds, including MnFe(P,As) and MnAs, have shown promising magnetocaloric properties.

  5. Heusler alloys, such as Ni-Mn-X (X = In, Sn, Sb), exhibit a strong magnetocaloric effect near room temperature.

  6. Some organic compounds, such as coordination polymers and organic radical compounds. These materials offer the advantage of tunable properties and can be chemically engineered for specific applications.

The most significant application of magnetocaloric materials is magnetic refrigeration. These systems offer an energy-efficient and environmentally friendly alternative to traditional refrigeration technologies without the use of harmful refrigerants, such as hydrofluorocarbons (HFCs) or chlorofluorocarbons (CFCs). Magnetocaloric refrigeration has the potential to be used in household refrigerators, commercial cooling systems, and air conditioning units. Other applications are cryogenic cooling for sub-zero chambers in medical research, superconductivity, and low-temperature physics; waste heat recovery, putting unwanted heat to work in a cooling application; and magnetic field sensors, sensing magnetic changes with a thermocouple or sensing temperature changes with a magnetic sensor.